Electric heater



Sept. 18, 1945. E. B. WILLIAMS ELECTRIC HEATER Filed April 9. 1943INVENTOR? EDMOND BRYAN WILLIAMS w A TTORNEY Patented Sept. 18, 1945ELECTRIC HEATER Edmond Bryan Williams, Litchfield, Coma, as-

signor to The Torrlngton Manufacturing 00., Torrington, Conn., acorporation of Connecticut Application April 9, 1948, Serial No. 482,473

7 Claims. (Cl. 2l9 39) This invention relates to improvements inelectric heaters, being particularly applicable to the smaller,portable, hand-held types of electric heaters suitable for use forexample, for defrosting purposes in high-altitude aircraft. Somefeatures of the improvements are, however, adapted for heaters ofconsiderably larger sizes whether of stationary, portable orsemi-portable types.

The requirements of a small hand-held defroster unit for aircraft, haveaccentuated the several inadequacies of older, existing portable typesof heaters for this usage; this applicant is fully aware of the manydesigns of smaller portable heater units such as hair driers and thelike, but most of those heretoforeavailable to the trade areinefllcient, slow in warming to the desired temperature, needlesslyheavy in weight, and difficult of manipulation. It is accordingly ageneral object of this invention to overcome the difliculties noted withrespect to the prevalent types of existing small electric heaters, andob- Jectively to attain a design which is light, easily handled, quickto warm to desired temperature, and offers a minimum resistance to theair stream from the fan, as a result of a novel disposition of theresistance conductors employed for air heating purposes.

Yet another object of the invention is attained in an improved mountingstructure or support for an electric heating element such as resistancewire, and which enables the installation of the unit in, or its removalfrom a fan housing, substantially as a separate unit.

Yet another object is attained in an improved arrangement of insulatingelements, means for mounting same, and an improved assembly ofresistance wire to such elements for the purposes, first, of minimizingresistance to the fan stream and secondly, of facilitating assemblyoperations in production of the heater.

Yet another object of the invention is attained in an improvedconstruction of housing for a fan and resistance element in a device ofthe class referred to, which makes for greater efficiency, quietoperation andeiiiclent delivery of a well confined stream of warm air,as for defrosting purposes.

Yet another object of the invention is attained in certain improvedstructural features pertaining to the manner of detachably assemblingthe housing for the fan and heating conductor, to a fan motor, and animproved expedient for providing an assembly of the type noted with adetachable handle or like manipulating member.

Further objects and advantages include an improved construction ofhousing for the fan and resistance element, particularly a novelarrangement of the inlet portion of the housing; an improved low costassembly provision through which the housing is supported from themotor, and an improved resistance-mounting spider secured to thehousing,

The foregoing and other objectives will more clearly appear from thefollowing detailed description of a preferred embodiment of the devicein a hand defroster for aircraft use, particularly when the descriptionis taken with the accompanying drawing, in which:

Fig. 1 is a side elevation of a complete hand defroster unit embodyingpresent features;

Fig. 2 is an end elevation as viewed from the front or air delivery endof the unit;

Fig. 3 is a somewhat enlarged vertical sectional elevation through thehousing for the fan, and showing the resistance element and itsmounting, as taken along line 3-3 of Fig. 2, and

Fig. 4 is a front elevation, in which certain of the elements are shownin section, of the structure of Fig. 3, as viewed along line 4-4thereof.

Referring now by characters of reference to the drawing, the devicecomprises as major elements, a small, compact fractional H. P. motorindicated generally at Ill. The motor I0 is preferably of an enclosedframe type, requiring no special provisions for ventilation or the likesince it usually operates for relatively short periods at a time.Accordingly, the end bell portions II at the rear, and I! at the front,are or may be imperforate. In keeping with standard aircraft practicethe motor I0 is of 24 volt D. C. type, and of moderately high speed.

Further major elementsinclude a fan i3, shown as a five-blade sheetmetal fan of propeller type, and which is secured as through a hubportion l4 and set screw I5 to shaft iii of the motor. By preferencelocated somewhat forwardly of the fan I3, is the resistance wiregenerally indicated at IT and mounted as hereinafter described.

As a housing structure for the fan and resistance element there isprovideda relatively short, tubular, preferably cylindrical sheet metalhousing, the body of which is indicated at 20. A pair of end rings orplates are provided as parts of the housing and are designated at 2|,being the backplate or ring, and 22, being the plate or end ring at thefront or discharge end of the housing. By preference both of the plates2| and 22 are secured to the end margins of the body 20 as throughcrimped joints 23 for the backplate and 24 for the foreplate or ring.Both of the rings 2| and 22 are for obvious reasons profusely perforatefor the purpose of offering a minimum of resistance to the flow of airthrough the housing. This is particularly true and necessary in the caseof the foreplate 22 which is of practically completely open aspect,except for a plurality of radial spoke-like portions 25, these beingillustrated as six in number. The extent of aperturing of the back plate2| is of less importance, because of other provisions for supplyingintake air to the fan, noted in the present example as a. peripheral rowof closely adjacent, rectangular inlet openings 26 (Fig. 1). These arearranged as a band of ports adjacent the rearmost margin of the body ofhousing 20, and are arranged closely to each other, being separated onlyby relatively narrow bridge portions 21. It will be noted that the bandof ports 26 is arranged in substantially the zone of the propeller typefan l3, the center line of the ports lying however slightly to the rearof the median transverse plane through the fan l3. It has been foundthat the provision of the ports arranged substantially as shown inrespect to the fan, results in an eificient and quiet arrangement, andserves to attain, as shown by careful trials, better characteristics ofthe fan stream delivered by the unit.

Support of the housing 20, the heating element and mounting therefor isconveniently effected, according to the present example, through aplurality of screws 30 extending through a centrally depressed portion3| in the backplate 2| of the housing, and threadedly engaging suitabletapped screw seats in the end bell I! of the motor. Since the housing 20is relatively short, the mounting of the housing to the end bell servesentirely adequately without the provision of any frame members common tothe housing and motor other than as described.

Proceeding now to the foreplate or end ring at the discharge end of thehousing, this element 22, preferably crimped to body 20 as noted, ischaracterized by a central imperforate zone 32 from which emanate thearms 25 which extend to and merge into the ring section 33 through whichattachment is or may be efiected to the end margin of the housing. Itmay be desired, however, and as shown, to utilize a separate grilleelement 34 although it will be understood that the grille element may,if desired, be formed integrally with and as a part of the foreplate 22.The grille 34, when utilized, may for example, be formed of quarter inchmesh wire cloth of a good quality, and the grille and foreplateassembled to the housing by a separate crimped band peripherallyembracing an upturned flange portion of the housing, the outwardlyextending flange portion of the ring or plate 22, and the grille.

As will best appear from Fig. 4 the area of each of the spoke-likeportions 25 is kept at a mimmum, with the now obvious purpose ofminimizing resistance to the fan stream. As the foreplate ispunch-formed or otherwise produced, the spoke-like portions or arms 25are of initially considerably greater area and, except for a minimum.-sustaining portion, are folded inwardly, i. e., toward the inside of thehousing body 20, each at substantially a right angle, thus resulting ininturned flanges 35, it being noted that these are of relatively thinmetal, and because of the bend imparted to each thereof, they areedgewise presented to the air stream from the fan l3.

Secured to each of the flanges 35 is a partly triangular foil or leafelement of a heat-resisting insulating material which, by preference,consists of a relatively thin leaf of mica, this material beingpreferred because of its unusual heat resistant and high electricalinsulating properties. Each of the foils 36 is riveted to one of theflanges 35 as by a pair of rivets 31, and so becomes virtually anextension of the associated flange 35 on each of the arms 25.

As a result of a number of trials of diiferent expedients for mountingthe resistance wire l1, and because of the advisability of minimizingthe metal fastening expedients for retaining the wire in position, therewas evolved the practice of providing each of the mica elements 36 witha deep, open-side recess or notch 40; the foils 36 being so mounted thatall of the notches are peripherally presented about the series of micaelements.

It is preference to employ a. nichrome wire as a resistance element,although any suitable equivalent thereof will serve the intendedpurpose; also, preferably, the wire ll is closely coiled as will readilyappear from Figs. 3 and 4'. In installing the wire on the spiderconstituted by the end ring arms, flanges 35 and associated insulation,the resistance wire is slightly stressed or tensioned as successivearcuate zones thereof are brought around and seated into the successivenotches 40 of the arcuate series of mica foils 36. Since, as is usual inaircraft practice, a single wire or grounded leg circuit is employed,the present assembly is or may be so wired; in this case, one end of theresistance conductor H, as indicated at 4|, is grounded to the end plateor ring. The opposite end of the element I! may be connected, as througha standard aviation single wire connector, indicated generally at 42,and including besides a fillister head screw 43, suitable mica washers44 or the like, the terminal screw thus being presented as at 45,exteriorly of the lower portion of the housing for the reception of aterminal clamping nut 46 providing a connection to lead wire 41. Actualphysical connection between the last mentioned end of the resistancewire, and the terminal assembly 42, is suitably effected by insertingthe end of the esistance wire in the slot of the screw head, the slotthen being closed by pressure so as firmly and permanently to clamp theend of the resistance wire in place in the screw head.

Further with reference to the spider employed as a unit mounting for,and including the resistance wire, it will appear particularly from Fig.3 as a preference to impart to the arms 25 and to flanges 35 formedtherewith, not only a radial trend but also to locate the center discportion 32 somewhat to the rear of the plane of the discharge end ofhousing body 20. The arms 25 and flanges 35 are accordingly given bothan inward and a backward direction. This tends to make a more rigidassembly, and to minimize shearing eflects on the mica foils as theresistance wire is tensioned thereabout, and results in a rugged anddependable spider mounting and construction. It will have been notedthat, although the resistance mounting spider is carried by the extremeend portion of the housing body 20 in the example shown, thisconstruction nevertheless lends itself admirably to assembly in anytubular, particularly cylindrical, air duct employed for electricheating of air in other applications. In

such case, the ring margin of the spider would desirably assume acylindrical form closely fitting nithin the inside of a cylindricalhousing such as It is particularly desirable in the case of a small handheld heater for aircraft defrosting purposes, to provide for thehandling of the unit with a minimum of effort, and to facilitate theoperator's quick service usage of it. Trials with different forms ofholders or handles for this purpose have lead to the adoption of apistol grip type of handle, indicated generally at 50, which is of arounded, palm-fitting contouring, as shown by Figs. 1 and 2, laterallymilled if desired, and provided on its upper surface nearest the frameill of the motor, with a dished motor-frame 'receiving seat Ii, intowhich is snugly saddled the central portion of the motor frame ill, thehandle structure being further shouldered if desired as at I! to obviateany tendency to fore-and-aft rocking displacement of the motor on thehandle. Assembly securement of the motor, and hence of the remainingoperative elements of the structure and the housing, is convenientlyeffected through a contractile band, of tempered spring steel forexample, indicated at 53, the opposite ends of which are ap'ertured soas laterally to engage the pistol grip handle Ill, and being securedthereto under tension as through a pair of screws or a through bolt ll.

As a convenience for the hanging support of the unit in a position forready access, there is provided a top loop element 55. This may beformed of a separate metal element embracing the top portion of .theband 83, but if desired may, as shown, consist of upwardly extendingapertured ear portions 58 provided with a hook receivin opening ll.

It is a preference, in order to facilitate on-andoff control of theunit, to provide in an easily accessible position, say for theforefinger of the operator's hand, a trigger type or toggle type controlswitch, the actuating element of which is indicated at 80, and which ispreferably so arranged in circuit as to control the energizationconcurrently, of both the motor i and the resistance unit ll. The switchproper (the mechanism of which is not shown since it forms per se nopart of the present invention) may be recessed in a suitable socketwithin the handle 50, and the circuit leads 'BI and '62 brought out at aconvenient zone in the lower portion of the pistol grip.

The function and usage of the portable defroster described, is thoughtto have been fully apparent from the description of parts and theirfunctional relation. It may however for completeness be noted that,incident to a period of use the unit is gripped as by handle 50, removedfrom support by withdrawing the hook-engaging eye element formed ofparts 56 from their support, switch member 00 being moved to circuitclosing position by the forefinger of the gripping hand. This movementof switch arm 80 serves to start the motor and to energize, with a quickheating effect, the resisting element II. The air supplying the fan IIis taken in some degree through the back plate ii to the extent that thelatter is apertured, but in important measure also through the row ofports 20, and is thence directed forcibly from that portion of the fanhaving the highest linear speed and greatest air deliverycharacteristics, directly across the resistance element H for heatingpures. It will now have appeared that the invention embodied in the formherein described, serves fully to attain each of the severalobjectsabove specifically set forth, and others implied from thedescription of parts and their function.

Although the invention has been described by making detailed referenceto a specific embodiment, the detail of description is to be understoodsolely in an instructive, and not in any limiting sense, since manychanges are possible within the scope of the claims hereunto appended.

I claim as my invention:

1. In a portable electric heating device, a motor, a fan driven thereby,a resistance element in the fan stream, a tubular housing of sheetmaterial about the fan and resistance element, the

fan being located in one end portion of the housing and the resistanceelement nearer the opp site end thereof, the housing being provided witha peripheral row of closely spaced, axially elongate, primary air inletapertures arranged as a band near the inlet end of the housing and in azone about the fan, the remainder of the housing body beyond said row ofapertures,-being imperforate, except for end openings to permit thepassage of air therethrough, and an end plate secured to the dischargeend of the housing body and provided with a plurality of spoke-like,inwardly projecting flanges, the resistance element being carried by andin insulated relation to said flanges.

2. In a portable electric heater adapted for use as a defroster or thelike, a motor, a fan driven by the motor, a resistance element locatedforwardly of the fan and a housing for enclosing the fan and resistanceelement, the housing including a substantially cylindrical body and apair of end rings each in the nature of a plate sufl'iclently aperturedto pass a current of air through the housing. the housing being providedwith a perimetral row of air inlet apertures of rectangular form, theapertures being located close to each other in the row, being elongatein a direction axially of the housing, and at least partly overlying thefan periphery, the end rings being crimped into securement with the endmargins of the housing body, a grille element disposed between theoutermost end ring and the housing body and assembled through crimpingof the adjacent end ring thereto, the last said end ring including aplurality of spoke-like elements each of substantially planar aspect andwith its planar portion directed inwardly of the housing in the form ofa flange presented edgewlse to the fan stream, a resistance element, andmeans by which the resistance element is supported in insulated relationfrom said flange portions.

3. In an assembly for the purpose noted, an electric motor, a fan, aresistance element, a housing for the fan and resistance element carriedby one end of the motor, a contractile band embracing the motor frame, ahandle of pistolgrip type, the contractile band being detachably securedto the handle, the handle bearing an acute-angled relation to the motorframe and housing afi'd having a hollow extension forwardly and upwardlyof its grip portion, a switch mechanism in the hollow-extension, and aswitch actuating member projecting forwardly of the extension in aposition to be actuated by the forefinger of the gripping hand of theuser.

4. In an electric heater housing for conducting a stream of air whilesame is being heated, a tubular sheet metal body through which thestream of air is to be conducted, a plate element securely crimped intoreinforcing attachment with one end of said body and being in the formor a ring provided with a plurality oi substantially radial arms, alsoextended axially inwardly of the tubular body, a foil oi'sheetinsulating material carried by each or said arms and projecting inwardlyfrom the end of the housing and edgewise to the stream of air passingtherethrough, each of said toils being provided with a notch in one ofits margins, and a length of resistance wire, for heatin: purposes,seated in said notches.

5. The combination and arrangement of parts as set forth in claim 4, butfurther characteriaed in that the resistance wire is seated intensionedmelation in the several notches of the insulating elements andis arranged in arcuate form substantially in a plane transverse to thedirection or air flow through the housing.

6. In an electric heater assembly of the general type described, amotor, a fan, a resistance element, a housing about the fan andresistance 2 element, a plate across one end or the housing and being ofsubstantially open construction inwardly of its periphery, the end platebeing secured along its periphery to the discharge end of the housing,and including a plurality of substan- 25 each having a trend depthwiseas well as radially 3Q of the housing, and thin, foil-like insulatingextensions on the several flanges, edgewise presented to the tandischarge stream and provided with open notches in which the resistanceelement is seated, whereby the flanges and extensions constitute asupport for the resistance wire and a reinforcing end frame for thehousing.

7. A ring support for a length of resistance wire or the like, as in anelectric heater, a tubular enclosure for the ring support, the supportbeing formed up as a spider having a closed continuous periphery adaptedfor mounting securement to mica secured to each of said flanges, eachfoil provided in its radially outermost portion with a deep recess ornotch, and a length of closely coiled resistance wire having spacedturns thereof seated in said recess whereby the resistance wire embracesthe notched edges of the foils under an appreciable tension, means formounting the spider, means for lmpellins a current of air across theturns of resistance wire and edgewise along the mica foils, thence outof the tubular enclosure, and means for supplying current to theresistance wire.

EDMOND BRYAN WILLIAMS.

